1) The purpose of this project is to refine a pneumatically powered impact noise generator whose peak level, rise time, and decay can be experimentally manipulated. Mechanical, acoustic and reliability parameters are being measured currently in preparation for (animal) exposure experiments. 2) Tone bursts are widely used in acoustic research, but a means of phase locking the zero crossing and manipulating rise time was needed, but not commercially available. Design of such a device was undertaken. 3) A closed system electroacoustic transducer having the ability to deliver high level, wide band minimum distortion sounds to the eardrum of guinea pigs has long been needed. Design of electronic circuitry, including predistortion, for use with condensor microphone speakers has been initiated. 4) Purpose is to develop a simple instrument with which significant speech discrimination test parameters can be manipulated. These parameters include peak level, long-term equivalent level, defined pink noise and speech spectrum noise for masking purposes and a means for modulating both.